Method of forming bellows folds



W. B. CLIFFORD METHOD OF FORMING BELLOWS FOLDS Sept; 15, 1931.-

3 Sheets-Sheet 1 Original Filed Oct. 4, 1924 mega 1 iv riff? Sept. 15,1931. w. B. CLIFFORD I METHOD OF FORMING BELLOWS FOLDS Original FiledOct. 4, 1924 3 Sheets-Sheet 2 Sept. 15, 1931. w. B CLIFFORD METHOD OFFORMING BELLOWS FOLDS Original Filed Oct- 4, 1924 3 Sheets-Sheet 5Patented Sept. 15, 1931 UNITED STATES PATENT {OFFICE ASSIGNMENTS, TOCLIFFORD MANUFACTURING 00., 01' BOSTON, MASSACHUSETTS,

A. CORPORATION OF DELAWARE METHOD OI FORMING BELLOWS FOLlJS Applicationfiled October 4, 1824, Serial 110.741.688. Renewed April 18, 1927.

The present invention relates to a method of forming bellows folds.

A well known type of thermostat consists of' a corrugated thin walltubehaving a series of bellows folds. metically sealed and filled with aliquid or gas which expands and contracts with variations intemperature, causing a similar expansion and contraction throughout thelength of the thermostat. This type of thermostat may be employed forany one of the variety of purposes where it is desired to control theoperation of .a valve or other instrumentality in accordance withvariations in temperature. The thermostatic tube is ordinarily composedof a tempered metal, such as a copper alloy, which tends to resume itsnormal dimensions after a forced expansion through heating of the liquidor gas contained therein.

This type of thermostat in actual ractice is formed by rolling a plaintube tween cooperating rolls positloned respectively within and withoutthe tube. These drawing rolls, through a series of successiveoperations, form a plurality of concentric folds or corrugations in aplain tube. An alternative method of forming the corrugations is tothread a plain tube upon a mandrel in such a manner that a series ofrelativel coarse spira corrugations are forme Thereafter t e tube isremoved from the mandrel and contracted in length to bring thecorrugations into close relation. In either case, the tube, after theformation of the corrugations, must be filled with the desired liquid orgas and hermetically sealed in order to prevent subsequent leakage ofthe contained liquid or gas therefrom. In actual practice, this type oftube is general- 1y sealed at the ends through the employment ofsoldered connections. There are several disadvantages inherent in thismethod of manufacture. The drawing operationslow, due to the method em-'ployed in orming the corrugations or bel-'.

is relativel lows folds. The tube must ordinarily be annealed at leastonce prior to completion of the corrugations and the smallest diameterof the tube which may be fabricated The tube is hertemperatures exceed300 F., due to the relav tively low melting point of the solder.

The principal object of the present invention is to devise a new andmuch improved method for fabricating thermostats of the above describedtype, by virtue of which the process of manufacture will be simplifiedand the quality of the resulting product materially improved.

With this and other objects in view, one feature of the inventionconsists in preforming a plain tube with a series of slightly rounded orbulged portions extending lengthwise of the tube, and thereaftersubjecting the tube to a longitudinal pressure suflicient to contractthe tube and sustaining the rounded or bulged portions by an in ternalpressure to cause the tube to freely fold or roll'up throughout theseportions as it contracts in length. In the simplest and most efficientform of the inyention yet devised, this preforming of the tube isaccomplished by supporting the outer wall of the tube at predeterminedspaced intervals and applying a preforming pressure from the inside 1nsufficient amount to stretch and cause the walls of the tube to bulgebetween the supports or forming members. This preformingis not carriedto a point at which the walls are ruptured or substantially weakened. Inactual practice, fluid is inserted within the tube and subjected topressure to first preform the tube and to thereafter sustain the wallsof the tube during the contraction in length. It will be obvious,however, that reforming of the tube might be accolnp ished in anydesired manner, and the preformed tube later sustained by an internalfluid pressure during the contraction in length. During the finalformation of the corrugations, suflicient internal pressure is exertedto maintain the walls of the tube throughout the preformed areas undertension, this pressure when properly coordlnated with the thickness ofthe tube, strength of the material and the length of the unsupportedportion of the wall causing the wall to fold up into a bellows fold orrounded corrugation rather than to flatten or crimp, as would otherwisebe the case. With this method the tube is initially divided intoexpanded or bulged portions of accurate and predetermined lengthmeasured off by the external spaced supports or forming members whichare locked to the tube due to the expansion of the tube therebetween.After the initial locking of the forming members to the expanded tube,the expanded portions are caused to fold into bellows folds by thecombined forces of internal pressure and axial contracting pressurewhile permitting the forming members or plates to move with the tube dueto their interlocked relation therewith, in a simple embodiment of theinvention this freedom of movement of the forming members beingaccomplished by releasing the forming members from spacers whichdetermine the initial spacing.

Another feature of the present invention consists in forming an annularflange upon one or both ends of a length of plain tubing, assembling afitting therewith and sealing the fitting to the flange in a manner toform a liquid or a gas tight joint, connecting the tube assembly with asource of fluid pressure through an opening formed in the fitting, andthereafter forming the corrugations or bellows folds as hereinbeforedescribed. In one form of the method, the liquid employed for creatingthe internal pressure may be the liquid used for filling the thermostatassembly. Upon completion of the operation therefore, the completedassembly is merely disconnected from the source of liquid pressure, theends sealed in a suitable manner, and the thermostat completed withoutsubsequent operations. The utilization of the liquid employed forfilling the thermostat in the operation of fabricating promotes economyand efficien y. as the filling of a preformed corrugated tube withliquid in a manner to completely expel all air or gas from within thetube may well be a tedious and diflicult operation.

The present method is not to be confused with certain prior suggestionswhich purport to disclose methods of forming hollow metallic articlesthrough the employment of an internal liquid pressure for forcing thearticle into conformity with an external mold. Although such methodshave been known and disclosed for many years, they have never achievedany measure of practical success for the fabrication of corrugatedtubing', in spite of the fact that the field for tubing formed in thismanner which is capable of withstanding repeated expansion andcontraction without failure is exceedingly great.

In the accompanying drawings illustrating the preferred form of theinvention, Fig. 1 represents a side view of a plain tube cut to theproper length and flanged at opposite ends; Fig. 2 is a viewillustrating the tube of Fig. 1 with the cap members applied to theopposite flanged ends to hermetically seal the interior of the tube;Fig. 3 is a view illustrating the complete tube assembly with the endssupported, the interior connected to a source of liquid pressure, andthe tube intermediate its ends rigidly supported at spaced intervals;Fig. 4 is a view similar to Fig. 3 illustrating the partial formation ofthe bulges or rounds in the tube, these bulges occurring in the areasbetween the points of rigid support; Fig. 5 is a view illustrating thenext step in the operation of fabricating the tube in which the latterhas been contracted through pressure exerted at one end, causing therounded areas to roll up between the points of support, as indicated;Fig. 6 is a View illustrating the thermostatic tube after the formationof the bellows folds has been completed, due to contraction in length ofthe tube; Fig. 7 illustrates a side view of a completed thermostatassembly filled with liquid and having the opening in one end scaled bya threaded plug; Fig. 8 is a side view partly in section illustrating amodified form of assembly prior to the formation of the corrugations. Inthis form the tube is opened at one end and sealed at the opposite end.Fig. 9 is a detail illustrating an elevation of a two part rigidsupporting member with the tube shown in section therein; Fig. 10 is aside elevation partly in section of a relatively simple form of jig foraiding in the formation of the bellows folds in the tube; and Fig. 11 isa cross section in elevation of the jig taken upon the line 1111 of Fig.10.

According to the present invention, the corrugations or bellows folds inthe thermostatic tube are produced by rigidly supporting the tube atspaced intervals throughout its length, subjecting the interior of thetube to an internal pressure properly coordinated with the length of thetube between supports, and finally completing the formation of thecorrugations through endwise pressure, tending to contract the tubelongitudinally while maintaining an internal pressure sufficient to keepthe preformed areas under tension and prevent crimping. The internalpressure initially applied to the interior of the tube may be sufficientto slightly round or expand portions of the tube between the rigidsupports but is insuflicient to rupture the walls of the tube. lVith thetube preformed in this manner, the tube is subjected to an endwisepressure to compel a contraction in length. During the application ofthis pressure, internal pressure on the tube is maintained in suflicientamount to compcl the walls of the tube to roll outwardly between therigid supports. This pressure should be substantially constant duringthe contraction of the tube and may be equal to or less than the initialpressure employed for bulging or rounding the tube. During thecontraction of the tube, the rigid and initially spaced supports arefree to move together, the position of the supports with relation to thetube being maintaine'dby locking of the supports to the tube through thebulged or rounded areas therebetween. The preforming or bulging of thetube between rigid supports locks the supports in initial uniform spacedrelation and avoids any additional spacing mechanism during the movementtogether. Any attempt to deviate substantially from the use ofcomsimilar material, with the clamped therebetween, provide a jointwhichbined pressures as outlined results in failure. The employment ofan internal pressure in suflicient volume to expand the bellows foldsresults in rupture of the walls after a partial formation of thecorrugations. An attemptto form the corrugations by the use of anendwise pressure with an internal pressure intended to actmerely as aliquid mandrel, without preforming, results in crimping or flattening ofthe corrugations, the walls of the tube tending to form in a seriesoffolds unless preformed and compelled to roll on a curve.

Referring to the illustrated embodiment of the invention, a tube 20 ofcopper alloyed with other material, such as zinc, tin, or similar orequivalent material, is cutto the desired length. The opposite ends ofthe tube are then flanged outwardly at 22 through a spinning or drawingoperation. The thermostatic tube blank so formed is next closed atopposite ends by heads or fittings 24. Each head comprises a sleeve 26having an inwardly projecting shoulder 28 engaging with the flange 22and clamped thereto by a head 30 threadedly connected with the innerface of the sleeve. The two parts of the head, preferably of steel or.flange rigidly.

is liquid or gas tight, even under relatively high pressures. Referringto Fig. 2, it willbe evident that the head at one end of the tube isslightly varied. In this case, the

sleeve 26 cooperates witha head 32 having an extension 34 providedwith-a liquid opening 36 communicating with the interior of the tube. Itwill be evident to those skilled the thermostatic tube blank the flangeis formed upon one end, the sleeves 26 next.

mounted, and the flange thereafter formed suitable jig with oppositeends of the tube curvedlines. tubeblank when (limited in Fig. 5. In'thisfigure, the areas of the tube between supports -ment is continued untilthe ri held rigidlyin alignment by heads 38 and 40. The head providedwith the opening 36 is connected to a source of liquid supply underpressure, indicated encrally at. 42. Surrounding .the walls of the tubeand spaced at uniform intervals are a series of rigid formers orsupports 44, which may be retained in spaced relation by virtue ofspacer members 46. As indicated in Fig. 9, each of the rigid supportsmay preferably comprise cooperating plates and 52 of tool steel orsimilar material which,- in assembled relation, fit closely about thetube blank 20. The cooperating plates are locked in assembled relationby oppositely disposed clips 54 and 56, which also serve to maintain theplates in spaced relation when the contraction of the tube blank hasbeen completed. Having assembled the thermostatictube blank as indicatedin Fig. 3, with opposite' ends held in alignment and the periphery ofthe tube throughout its length rigidly supported at spaced intervals,the interior of the tube is filled with a suitable liquid indicated atthrough the opening 36. The pressure of this liquid is increased to apoint at which the walls of the tube between therigid supports arerounded or bulged, this preformi1 ig ;:,ofthe tube being exaggerated inFig. ls- 1twill be evident that this preforming of the tube betweenpoints of supports locks the rigid forming and supporting members inspaced relation throughout the length of the tube and thereafter permitsremoval of the spacer members 46. Having thus preformed the thermostatictube blank with a series of successive rounded or slightly bulged areasbetween supports and removed the spacer members, the assembly as a wholeis subjected to a sufiicient endwise pressure to compel contraction inlength of the tube. During this endwise movement,the internal pressureis maintained in sufficient amount-to maintain the walls of the tube intension and compel the metal between supports to roll along Theapproximate shape of the partially contracted is inhave been rolledoutwardly and the supports due to the contraction of the tube,- moveinto closer relation. Duri the contraction of the tube, the internalpressure is maintained substantially constant through the employment of.arelief. valve or an accumulator. In actual practice in the art that inthe actual production :of

tion of t e arrow in Fig; 5, while'rigidly ;maintaining the opposite endin .a fixed contraction of the tube is accomplished moving the head 38inthe direcposition. The endwise contracting movegid supports have beenmoved into the relatlve positions with the side portions 62 of theclamps in contact with one-another limiting further movement of thesupports together. The completed thermostatic assembly is wellillustrated in Fig. 7, the tube being provided with a series ofregularly spaced corrugations or bellows folds, the space between eachtwo folds corresponding to the thickness of the rigid supports andapproximating the outer thicknessof the folds. I will be evident,furthermore, that the individual folds are of substantial depth and thatt-he extreme diameter of the folds is materially greater than theoriginal diameter of the tube and that the side walls of the folds arenormal to the axis of the tube. As will. be evident from an inspectionof Fig. 7, the thermostatic assembly, after being disconnected from thesource of liquid pressure, is closed with a plug which threads withinthe opening 36 and engages with the tapered end 72 to tightly close thesmall opening 74c.

Although obviously any desired liquid may be employed for maintainingthe internal pressure upon the tube, it is preferable to employ theliquid which is to be later used in the operation of the thermostat.This avoids the necessity of emptying the tube and refilling it with adifferent liquid. The refilling of a corrugated tube of this character,especially where the corrugations are relatively small and closelyspaced, may be a slow and tedious operation, due to the formation of airpockets in the folds. If these pockets of air are not completelyexpelled durin the filling of the tube with liquid, the subsequentoperation of the thermostat is irregular and faulty.

It will be evident to those skilled in the art that the formation of thecorrugations in the manner above described is accomplished withoutimposing undue strains uponthe metal or without imparting such a temperto the metal that it becomes brittle and liable to failure underrepeated expansion and contraction of the thermostat. Furthermore theformation of the corrugations may be completed in a continuous operationand without the necessity of annealing the tube prior to its completion.An alternative form of thermostatic assembly is indicated in Fig. 8. Inthis construction, the blank instead of being cut from a previouslyformed tube is drawn from a sheet of the desired thickness to form adeep drawn tube 80 with a closed bottom portion 82. Having formed thetube in this mannor, the opposite end is provided with a flange 22 and atwo-part head 24 mounted thereon, the portion 32 of the head having theusual opening 36 for connection with a source of liquid supply 42. \Vhenthe assembly is inserted in the usual jig, the closed end of the tube isassembled with a cap 83 having a recess 84 with reentrant or outwardlycurved side portions. When internal pressure is applied to the tubeblank, the end portion of the tube adjacent the cap is bulged out totill the recess 84, looking the cap rigidly to the tube. Thereafter theformation of the corrugations is conducted in the manner previouslydescribed. lVith this method, the completed thermostatic assembly issimilar to that illustrated in Fig. 7 but requires a hermetically sealedjoint at one end only of the tube. Furthermore the formation of the lipat one end is eliminated and the cap mounted on the closed end of thetube is made in a single piece. In forming thermostatic assemblies ofcertain dimensions, the method illustrated in Fig. 8 is probablysomewhat more efficient than the method previously described.

A form of apparatus adapted to carry out the new and improved process ofmak ing thermostatic assemblies is'illustrated in Figs. 10 and 11. Asindicatedin these figures, the tube assembly is mounted between twoheads 38 and 40. Each of these heads is recessed to receive and closelyfit the opposite end caps upon the tube assembly. The head 38 isswiveled in the end of a lead screw 90 threadedly mounted in an endbearing 92. The end bearings 40 and 92 are rigidy maintained inpredetermined relationship by angle bars 94 which extend lengthwise ofthe jig at each corner and are secured at opposite ends to heads throughbolts 96. Each of the heads 40 and 92 is of rectangular outline and ofsuch a, size that the inner faces of the angle bars 9 when secured tothe heads function as guides for the longitudinal movement of the rigidsupports. As indicated more particularly in Fig. 11, the clamps 54 and56 contact with the inner faces of the angle bars and slide thereon,these bars maintaining the supports in accurate alignment with the tubebut permitting a free longitudinal movement thereof. The head 40 isprovided with a centrally disposed passage 98 communicating with arecess, in which the end cap is seated. The passage 98 receives the endof a pipe 100 which is threaded within the opening 36 to form a liquidtight joint. The supporting members are maintained in spaced relation bya series of spacer rods 46 which are inserted between the supportingplates upon opposite sides of the tube assembly. After the initialinternal pressure has been applied to expand the tube and the spacerrods removed, the latter is contracted by rotating the lead screw 90 toexert an endwise pressure upon the tube and cause a bodily movement ofthe head 38 toward the stationary head 40..

During this movement, the supporting plates locked to the tube movetherewith toward the. head 40 and toward one another. In the actualoperation two or more of the angle bars 94 are first removed from theheads. The tube blank is inserted with the end caps received in therecesses in the heads 38 and 40. Thereafter the supporting plates arepositioned about the tube, clamped together, and the spacers inserted.The angle bars are then secured to the heads and the source of liquidpressure connected to the open end of the tube assembly. After theinitial bulging of the tube has been accomplished, the spacer membersare removed and the tube is then contracted, while maintaining asubstantially constantinternal pressure. Although any desired form ofmechanism may be employed for creating the internal pressure within thetube and maintaining this pressure constant during the contractingmovement, this may be conveniently accomplished by a hand op,-

erated pressure pump 102 having a screw operated plunger 104 with apressure gauge indicated at 106, which is intended to accuratelyvisualize the internal pressure within 'the tube.

By a suitable manipulation of the hand operated pump, the desiredpressure may be applied initially and maintained during the contractionof the tube. Obviously, as

the tube is contracted in length-and the cor-- rugations formed, thecapacity is decreased and the pump must be backed off to maintain asubstantially constant pressure.

T In actual practice, a phosphor-bronze tube having an outside diameterof 3/8 and with walls 10/1000" thick has been provided with rigidsupports spaced 3/16 apart between the opposite walls of successivesupports, each disk being 32/1000" thick. The application of an initialpressure approximating 2500 pounds per square inch preforms' or bulgesthe tube between sup orts. Thereafter an endwise pressure in su cientamount to contract the tube is applied while maintaining an internalpressure of 2000 pounds per square inch approximately. The initialpreforming-pressure actually exerts a slight stretching action upon thewalls of the tube, whereas the sustaining pressure subsequently employedmerely compels the walls of the tube to fold outwardly in the preformedareas and prevents crimp ing or folding of the corrugations betweensupports. It is the coordination of the internal pressure initiallyemployed for preforming the tube between supports and thereafter thecombination of an internal sustaining pressure with endwise pressure forrolling up the tube in the preformed areas which accomplish the desiredresult. Neither of these forces operating independently will suffice forthe purpose.

It must be evident to those skilled in the art that although theformation of certain hollow metallic shapes may be successfully carriedout by expanding a tubular blank into an external mold through internalpressure exerted upon the blank, this general mode of operation cannotbe employed for the production of thermostatic tubes having relativelydeep and closely spaced bellows folds; The desirability of athermostatic element of this character having a.

large number of closely spaced bellows folds in a given length isself-evident, as the distortion of the individual folds for any givenexpansion of the thermostatic element is in inverse ratio to the numberof folds.

It will be evident from the foregoing description that the formation andcompletion of bellows folds in a thin wall tube is accomplished in oneoperation by insuring an accurate initial spacing of the formingmembers, locking the forming members to the tube in such initial spacedrelation through expansion of the tube by internal fluid pressure, andthereafter, by the combined forces of internal fluid pressure andendwise contracting pressure, causing the expanded portions to fold upinto corrugations between the forming members or encircling supports,the metal being enabled to flow freely during the forming operation bypermitting the forming members to move be quickly and economically made,and

which has a resultant long life due to the substantially equal capacityto withstand a relatively great number 0 expansions and contractions.

The invention having been described, what is claimed is: 1. The methodof forming a corrugated tubular thermostat which consists in forming aflange on the open end of a tubular blank, assembling a two part headabout the flange with an opening therethrough for the introduction ofliquid, corrugating the tube blank while supported internally bypressure exerted through the fluid introduced through the opening in thehead, and finally sealing the opening in the head.

2. The method of making a corrugated tubular thermostat which consistsin mount- -ing heads upon opposite ends ofa tubular blank, connectingthe blank to a source of fluid pressure through an ope'ningin one of theheads, forming corrugations while supporting the walls of the tubethrough in ternal fluid pressure introducedthrough the opening in thehead, and finally sealing the opening in the head.

3. The method of making a bellows which consists in roviding a plaintube w1th opposite ends hermetically sealed except for an openingthrough one end, connecting the openin with a source of liquid pressure,assemb ing a series of divisible plates lengthwise of the tube, each ofthe plates having an opening correspondlng to the extrior diameter ofthetube, malntaimng the plates rigidly in alignment with the axis of thetube, subjecting the tube to an internal li uid pressure to sustain thewalls of the tu be against collapse, thereafter sub ect1ng the tube toan endwise contracting pressure while permitting the plates to movelengthwise, of the tube, and thereafter sealing the opening in the tube.

4. The method of making a bellows which consists in forming a plain tubewith a closed bottom ortion, forming a flange on the open end 0 the tubeopposite the bottom portion, assembling a head upon the flanged end ofthe tube with an o ening extending therethrough, mounting a ead at theopposite end of the tube with the closed end of the tube received in arecess in the head, and subjecting the tube to internal fluid pressureto distort the closed end of the tube and lock it firmly within thehead.

5. The method of forming a series of bellows folds in a tubular blankwhich includes flanging the open end of the blank, assembling a head onthe flange to seal the open end of the blank, the head having an openingtherethrough communicating with the interior of the blank, connectingthe interior of the blank through the opening in the head with a sourceof fluid supply, supplying fluid under substantial pressure to theinterior of the blank through the opening, forming a series of bellowsfolds while maintaining the internal fluid pressure, and thereafterdisconnecting the formed blank and attached head from the source offluid supp The method of forming bellows folds from thin wall tubingwhich consists in positively locating s aced forming members lengthwiseof a tu e, expanding the tube to lock the members thereto in the initialspaced relationship, and thereafter causing the tube to expand outwardlyinto corrugations between the members by the combined forces of internalfluid pressure and axial contracting pressure, while enabling the metalto flow freely during the forming operation by permitting the formingmembers to move toward each other unrestrained by the spacing means butin their interlocked relation with the forming folds.

7. The method of forming bellows folds in tubing which consists inassembling a series of separable forming members about a tube and inspaced relation lengthwise thereof, positively retaining the members inthe initial spaced relation, locking the members to the tube while somaintained, releasing the members to permit movement lengthwise of thetube, and thereafter expanding the tube unrestrained by the spacingmeans into bellows folds between the members by the action of aninternal fluid pressure'while permitting the forming members to movetoward each other in a manner governed by the contraction of the tube towhich the members are locked.

8. The method of making bellows folds in thin wall tubing which consistsin assembling the tube'within a series of separable forming membersfixedly spaced lengthwise of the tube, locking the members to the tubein the spaced lengthwise relationship, and thereafter expanding the tubeinto circumferential folds between the members by the combined forces ofinternal fluid pressure and endwise contracting pressure whilepermitting the members to float unrestrained except for theirinterlocked relation with thetube during the contraction thereof.

9. The method of forming bellows folds tin tubing which consists inapplying and sealing a head having a passage therethrough upon the openend of the tube, assembling the tube with the thus connected head withina series of spaced forming members collapsible in an axial direction,connecting the passage in the head with a source of fluid pressure, andforming bellows folds through the combined forces of internal fluidpressure introduced through the passage and endwise contracting force.

10. The method of forming bellows folds in tubing which consists inapplying and sealing a head having a passage therethrough upon 'the openend of the tube, assembling the tube with the thus connected head withina series of spaced forming members collapsible in an axial direction,connecting the passage in the head with a source of fluid pressure,forming bellows folds through the combined forces of internal fluidpressure introduced through the passage and endwise contracting force,and removing the completed bellows with attached head from within theforming members.

11. The method of forming bellows folds in tubing which consists inmounting a permanent head with a passage therethrough on the open end ofa tube, assembling the tube with the mounted head within a series ofspaced forming members collapsible axially of the tube and with thepassage in the head connected to a 'source of fluid pressure, thereafterexpanding the tube into bellows folds between the forming members by thecombined forces of internal fluid pressure introduced through thepassage and an endwise contracting force, and removing the bellows withmounted head from within the forming members.

12. The method of forming bellows folds in thin wall tubing comprisingthe assembly of a series of separable forming plates insure fixedlyholding the platesin spaced ,parallel relation, expanding the tubebetween the plates by internal pressure introduced therein, afterlocking of the plates to the tube through expanding removing the membersfor insuring the spacing and parallelism to permit freedom of movementof the plates with the tube, due to their intprlocked relation therewithand thereaf er deepening and narrowing the bulges be tween the platesthrough the combined forces of internal fluid pressure and endwise-contracting pressure while guiding the plates to move in axialalignment and prevent axial buckling of the tube in process.

13. The method of forming bellows folds which consists in mounting ahead on the open end of a tube to provide a projecting annular shoulder,the head having a passage therethrough communicating with the interiorof the tube, maintaining the passage in the head sealed throughengagement with the shoulder, surrounding the tube with a series ofspaced forming members, and there after expandin the tube bellows foldsbetween the members by the combined forces of internal fluid pressureand endwise contracting pressure. J

14. The method of forming bellows folds in thin wall tubing, whichcomprises assembling the tube within a series of positively spacedforming members, niaintaining the tube at one end in communication witha source of fluid pressure, expanding the tube between the formingmembers without contraction of the tube, and thereafter deepening andnarrowing the expanded portions through maintenance of the internalpressure and application of an endwise contracting pressure to the tubewhile enabling the metal to flow freely during the forming operation bypermitting the forming members to move toward each other unrestrained bythe spacing means but in their interlocked relation with the tube.

15. The method of forming bellows folds in thin wall tubing whichcomprises assemblin a tube within a series of axially spaced ormingmembers held against axial movement lengthwise of the tube, expandingthe tube between the forming members while so held against axialdisplacement, completely releasing the members to permit freedom ofmovement of the members with the tube, and when so released deepeningand narrowing the expanded portions in the tube through the combinedforces of internal fluid pressure and endwise contracting presbellowsfrom thin walled tubing, of locking a series of formin while enablingthe metal to flow sure while enabling the metal to flow freely durlngthe forming operation by permitting the forming members to move towardeach other unrestrained by the spacing means but in their interlockedrelation'with the tube.

16. In themethod of forming a. flexible the steps members to the tube inexact spaced relation by differences in diameter of the tube at .andbetween the several forming members and then forming bellows foldshaving a substantially equal capacity to withstand a relatively greatnumber of expansions and contractions by folding the metal between saidmembers under the combined action of internal fluid pressure and anaxial contractin pressure reely during the formlng operation bypermitting the forming members tomove toward each other unrestrainedexcept for their interlocked relation with the formi folds.

17. In the method 2% forming a flexible bellows from thin walled tubing,the steps of locking a series of forming members to. the tube in spacedparallel relation byproducing differences in. diameter of the tube atand between the several forming members through expansion of the tubetherebetween and then forming bellows folds having a substantially equalcapacity to withstand a relatively great number of expansions and.contreictions by folding the metal between said members under thecombined action of internal fluid pressure and an axial contractingpressure while enabling the metal to flow freely during the formingoperation by permitting the forming members to move toward each otherunrestrained except' for their interlocked rela tion with theforming'folds.

18. In the method of forming .a flexible bellows from thinwalledtub-ing, the steps of looking a series of forming members to the tube inspaced relation by differences in diameter of the'tlibe at and betweenthe several forming members and-then forming bellows folds having asubstantially equal capacity to. withstand a relatively great -number-of-expansions and contractions by folding the ;metal between saidmembers under the combined action of internal fluid pressureand an axialcontracting pressure while enabling the metal to flow freely during theforming operation by permitting the forming members to move toward eachother, guided with the openings in the members maintained in alignmentbut otherwise unrestrained except for the interlocked relation of themembers with the forming folds.

thetube, assembling the forming members about a tube in suchpredetermined and spaced relationship, locking the tube to the initiallylocated forming members by ex pansion of the tube through internal fluidpressure and thereafter folding the metal between themembers by thecombined action of internal fluid pressure and an axial contractingforce after having freed the members from control of the spacing meansto permit movement of the members. toward one another in a mannergoverned entirely by their interlocked relation with the forming foldsof the tube.

20. In the method of forming a flexible bellows from thin walled tubing,the steps of locating a series of forming members in predeterminedspaced relation about a tube to be formed, locking the tube to thespaced members by expansion of the tube therebetween and forming bellowsfolds by the combined forces of internal fluid pressure and an axialcontracting pressure while allowing said members to float with the tubeduring contracting unrestrained by the locating means.

21. The method of making bellows which consists in assembling apermanent fitting with a tubular blank, locating the blank within aseries of spaced forming members, subjecting the blank to internal fluidpressure to lock the fitting thereto through distortion of thetubularblank in the region of the fitting, expanding the tube intocircumferential folds between the forming members by the internal fluidpressure and an endwise contracting pressure, and thereafter removingthe formed bellows and attached fitting from the forming members.

22. The method of making a bellows which consists in hermeticallysealing a tube with a permanent head having a restricted liquid openingthrough one end, connecting a source of fluid supply under pressure tothe opening, providing the exterior of the tube with a series ofencircling supports spaced lengthwise of the tube, exerting an internalfluid pressure to sustain the walls of the tube, and subjecting the tubeto an endwise contracting pressure while permitting freedom of movementof the supports lengthwise of the tube and maintaining the internalfluid pressure.

23. The method of making a bellows which consists in forming a plaintube, sealing the tube except for a restricted opening therethrough bythe application of a permanent fittting, connecting theopening with asource of fluid pressure, assembling about the tube a series of formingmembers each having an opening corresponding to the outer diameter ofthe tube, maintaining the members in alignment, subjecting the tube toan internal fluid pressure to sustain the walls of the tube between thesupports, subjecting the tube to an endwise contracting pressure whilepermitting the members to move lengthwise of the tube in alignmenttherewith and maintaining the internal fluid pressure during thecontracting movement.

24. The method of forming bellows folds which consists in assembling aseries of twopart plates in spaced relationship about a tube, lockingthe two parts of each plate rigidly in assembled position, locatingbetween successive plates and upon opposite sides of the tube spacermembers for insuring both accurate spacing and parallelism of theplates, While thus fixedly maintained by the spacer members expandingthe tube between the plates through the employment of internal fluidpressure to lock the plates to the tube in initial position,manipulating the spacer members to free the plates and permitunrestrained movement of the plates axially with the tube due to theirinterlocked relation therewith, and thereafter deepening and narrowingthe expanded portions into bellows folds through the combined forces ofinternal fluid pressure and endwise contracting pressure.

In testimony whereof I have signed my name to this specification.

WALTER B. CLIFFORD.

